1. Field of the Invention
The present invention relates to a bus bar arranged to be electrically connected with the end portions of a plurality of conductive lines led out from a coil, and a process for producing the same.
2. Description of the Related Art
A press-molded, strip-shaped conductor is commonly used as a bus bar. A strip-shaped conductor is usually formed by punching a metal plate into an intermediate member with a certain shape laying out a strip-shaped conductor, and then bending a certain portion of said intermediate member e.g. JP-A 2000-333400.
Further, in addition to the strip-shaped conductor, a rotating electrical machine is disclosed JP-B 3650372, which uses a conductive line as a connecting conductor bus bar. The connecting conductor disclosed in JP-B 3650372 is formed by bending a conductive line with a circular or rectangular cross section into a certain shape. Specifically, a ring-shaped receiving portion, and a terminal portion for coil connection protruding from four places of the receiving portion toward the external diameter direction in a radial shape are formed by bending a single conductive line having a circular cross section.
The terminal portion for coil connection is formed by bending and folding the conductive line by 180 degrees at a front end. In order to prevent the folded conductive line from being spread again, the base of the terminal portion for coil connection is joined by TIG welding. On the front end of the terminal portion for coil connection, a ring-shaped portion is formed for inserting a lead line of the coil. Also, a connecting conductor formed by making the receiving section level in the diameter direction into a flat shape is disclosed as well.
In the rotating electrical machine, three connecting conductors are received in a ring-shaped holder. The holder has three receiving grooves with different depths, arranged in a concentrically circular form, where receiving portions of each connecting conductor are respectively received.
Generally, a bus bar has protruding terminals formed on multiple places, and therefore its layout form is complicated. Accordingly, when a bus bar is formed by punching a metal plate into an intermediate member to produce a strip-shaped conductor, metal scraps are generated after the punching process and causes a decrease in the yield rate. Various studies regarding the shape of the bus bar or the positioning of the intermediate member when punching the metal plate are being conducted in order to improve the yield rate; however, the current situation is that several tens of a percent of metal plate are being wasted.
In such regard, when producing a connecting conductor by using a conductive line as in JP-B 3650372, metal scraps are not generated and the problem of yield rate as in the strip-shaped conductor does not occur.
However, since the connecting conductor in JP-B 3650372 forms the terminal portion for coil connection only by folding the conductive line, it requires welding of the base portion, which is a disadvantage in workability. Also, the connecting conductor is difficult to be received in the holder due to the thickness of the terminal portion for coil connection, which makes it difficult to handle compared to the strip-shaped conductor. Further, in the terminal portion for coil connection of JP-B 3650372, a plurality of coil lead lines are simultaneously inserted to the end portion for coil connection, either caulking or welding is required, and manual operations or arrangements of complex manufacturing devices or processes are required.